Photosynthesis drives solar
cell

August 25/September 1, 2004

Plants and photosynthetic bacteria contain
molecules that convert photons to energy very efficiently. The trick to
harnessing these molecules for solar cells is marrying these relatively
delicate molecules with electronics.

Researchers from the Massachusetts Institute of Technology, the
U.S. Naval Research Laboratory, and the University of Tennessee have mixed
biology and electronics in solar cells that use photosynthetic spinach
leaf molecules or photosynthetic bacteria to convert light to electricity.

When light shines on the spinach leaf molecules and photosynthetic
bacteria they produce an electrical current that is captured by electrical
contacts.

The internal quantum efficiency of the researchers' first-generation
prototypes is 12 percent. The method has the potential to exceed a power
conversion efficiency of 20 percent, making it as efficient as today's
commercial solar cells, according to the researchers.

The method could be used to fabricated solar devices on plastic
and other thin, flexible surfaces using inexpensive spray-on techniques.
The method could eventually be used to make large-area photovoltaic cells
and ultra-fast photodetectors, according to the researchers.

The researchers' prototype consists of a self-assembled layer
of the photosynthetic molecules mixed with surfactant peptides, covered
with an organic, semiconducting protective coating, and sandwiched between
metal contacts. Surfactant peptides are soap-like molecules.

The researchers are working on improving the device's efficiency
and lifetime.

Molecular photovoltaic devices could be used practically in five
years, according to the researchers. The work appeared in the June 9,
2004 issue of Nano Letters.